How is ureteropelvic (UPJ) junction obstruction diagnosed before and after birth?

  • An ultrasound exam before a baby is born can show a UPJ obstruction. As urine gets backed up due to blockage, the kidney swells beyond its normal size, a condition known as hydronephrosis.
  • Once the baby is born, tests that measure how well urine is being produced and drained include:
    • Blood samples and urine samples such as blood urea nitrogen (BUN) and creatinine tests provide clues on how well the kidneys are filtering the blood.
    • An intravenous pyelogram (IVP) injects a dye into the bloodstream that is then traced by X-ray as it flows through the kidney, renal pelvis, and ureter.
    • A nuclear renal scan uses a radioactive substance instead of a dye, and can be traced with a special camera. This shows the functioning of the kidney and how much blockage may be present.
  • Computed tomography (CT) and magnetic resonance imaging (MRI) scans can show obstructions in the kidney, as well as the structure of the kidneys, ureters, and bladder.

Last reviewed by a Cleveland Clinic medical professional on 07/27/2017.


  • Grasso M III, Caruso RP and Phillips CK: UPJ Obstruction in the Adult Population: Are Crossing Vessels Significant? Rev Urol. 2001 Winter, 3(1): 42-51. Accessed 8/1/2017.
  • National Institute of Diabetes and Digestive and Kidney Diseases. Urine Blockage in Newborns Accessed 8/1/2017.

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